Transcript Slide 1
Australia: Water and Soil Through (Pre) History David Radcliffe University of Georgia Published in 1994 3-part series on Australian TV in 1998 www.abc.net.au/science/future/default.htm Tim Flannery is Director of South Australia Museum Future Eaters • Part One – An Infinity Before Man – Geology and ecology of Australia before man arrived • Part Two – Arrival of the Future Eaters – What happened when the aborigines arrived • Part Three – The Last Wave – What happened when the Europeans arrived Early Geology • Australian continent drifted north as the Earth cooled – Stable climate with very little glaciation – “Did you have a good ice age?” • Did not collide with other continents – Little volcanic activity or mountain building • Resulted in infertile soils • Isolated continent (Galapagos on steroids) www.lonelyplanet.com Uluru www.photoway.com/fr/dest/AUST96_30.html Infertile Soils • Tim Flannery, Taming of the Fire, Australian Broadcast TV – “If you want to understand the history of this continent there's no better place to come than here to Uluru. – The timeless rounded features of the rock show that it hasn't been disturbed for hundreds of millions of years, there's been no volcanoes, no mountain building, no ice age here to rejuvenate this place and as a result the soil here is old, leached and exhausted. – All that's left really is just sand." Toowoomba Murray-Darling Basin accounts for 40% of agricultural income and 75% of irrigated land El Nino • El Nino Southern Oscillation effect (ENSO) • 2-7 year cycle of drought and rainfall • Australia is the only continent where the overwhelming influence of climate is not an annual cycle Under normal conditions, trade winds pile up ocean waters to the west and upwelling occurs to the east – warm wet air rises from eastern Australian Under El Nino conditions, trade winds weaken, warm water moves back east – dry air descends on eastern Australia www.pmel.noaa.gov/tao/elnino Negative SOI indicates an El Nino (drought) year http://www.bom.gov.au/climate/current/soi2.shtml Biodiversity • Theory: greatest biodiversity develops in low-resource (water & soil), stable environments – Organisms survive better by cooperating – Enough time for evolution of organisms to find a “niche” • Australia has greater biodiversity than other larger continents – Plant species in Australia: 25,000 – Plant species in Greater Europe: 17,500 Niche Ecology Examples • Kangaroo • Koala bear • Banded stilt Kangaroo • Kangaroo is world’s largest marsupial • Very efficient energy user – No other animal this big hops – Energy is recaptured in each bound, in the tendons of its legs – like a pogo-stick – Each leap pushes its gut back, drawing air into it’s lungs – saving it from using chest muscles to breath • Low reproductive rate • Female is fertile only during ENSO periods of high rainfall Eastern Grey Kangaroo www.giftlog.com Koala Bear • Diet consists entirely of Eucalyptus tree leaves – Lives it’s life in these trees – Leaves have toxins to discourage less specialized foraging animals • Very energy efficient – Slow moving like a sloth – Low rate of reproduction – Relatively small brain • Brain is one of the greatest energy users of all organs • In man, the brain is 2% of weight but uses 17% of energy www.giftlog.com Banded Stilt • Familiar bird along the coast but never seen to breed • March 1989 banded stilts disappeared from usual haunts • About 100,000 birds found nesting near Lake Eyre in South Australia • Lake was filling to a 15year high as a result of a period of ENSO rainfall The Slater Field Guide to Australian Birds www.lonelyplanet.com Banded Stilt • After hatching, the young were tended by the males – Hatchlings left the breeding area and grew quickly on a rich diet of brine shrimp – After only 3 weeks the young could fly • Only 2 weeks after first eggs were hatched, the female was nesting again • Breeding cycle adapted to ENSO – Can go a decade without breeding The Slater Field Guide to Australian Birds Future Eaters • Part One – An Infinity Before Man – Geology and ecology of Australia before man arrived • Part Two – Arrival of the Future Eaters – What happened when the aborigines arrived • Part Three – The Last Wave – What happened when the Europeans arrived Aborigines • Conventional view – Primitive civilization – Did not develop agriculture or cities – Nomadic – Few tools – Little impact Aborigines • Man evolved first in Africa and spread to other continents – Coevolved with megafauna species still seen today in Africa – Serengeti Plain (think Lion King) – Predator-prey arms race http://www.connectravel.co.ke/Serengeti.jpg Aborigines • Aborigines arrived in Australia at least 40,000 years ago – Came over water from Southeast Asia – By comparison, man arrived in New Zealand about 1,000 years ago • At that time there were a number of megafauna grazing species in Australia – Large areas of grasslands – Grazing megafauna recycled nutrients from grasses to soil Diprotodon Megafauna Extinction • Megafauna disappeared from Australia shortly after aborigines arrived – Climate or man? – “The greatest danger that a species faces in a rapidly coevolving ecosystem is the loss of contact with its competitors” • Megafauna had no defenses against man • Without megafauna nutrient cycling broke down and grasses disappeared and replaced by forests and deserts • Short, rich period for aborigines followed by disaster Aborigine Adaptation • Aborigines were the first Future Eaters – Consumed resources more rapidly than they could be replenished • “The story of how the first future eaters recovered from this disaster - is one of humanities greatest triumphs” • Long stable period (40,000 years) after megafauna extinction for aborigines to adapt – Developed complex relationship with ecosystem Aborigine Adaptation • Adapted to make it through the driest periods and take advantage of the wet periods – Did not develop agriculture because it was not sustainable given El Nino climate – Nomadism allowed aborigines to move to water and animals – Used fire to burn forests, recycle nutrients, and provide forage for animals – “fire-stick farming” – Few tools because they had to be mobile – Low population density – Social unit was small tribe consisting of a few families Aborigine Adaptation • Challenge was genetics – How to avoid inbreeding when your social unit is a small tribe • Solution was great tribal meetings during ENSO wet periods – Gathered in areas where food and water available – Marriages arranged between members of different tribes – Taboos prevented marriage within tribes – Elaborate ceremonies renewed bonds between tribes – Oral exchange of information on resources • Religion codified rules and was the knowledgebase passed from generation to generation Aborigines • Revised view – Highly evolved civilization – Nomads because agriculture was not sustainable – Few tools because these reduced mobility – Elaborate knowledge of ecosystem embodied in religion – Large impact Future Eaters • Part One – An Infinity Before Man – Geology and ecology of Australia before man arrived • Part Two – Arrival of the Future Eaters – What happened when the aborigines arrived • Part Three – The Last Wave – What happened when the Europeans arrived Arrival of Europeans • First contact occurred in 1688 with large number of Europeans arriving in early 1800’s • Aborigines suffered massive die-offs – Some killed in conflicts – Most killed by European diseases – Typhus, influenza, small pox, measles, etc. • Why didn’t the reverse happen? – Why didn’t Europeans die of aborigine diseases? European Diseases • Guns, Germs, and Steel by Jared Diamond • Most powerful diseases develop where you have: – High population densities – Contact with herding animals (source of diseases) • London a huge breeding ground for disease • Europeans developed some resistance to these diseases and survived • When Europeans arrived on other continents, locals had little resistance and died European Development • Australia was used as a place to send convicts from overflowing English debtor prisons – 1788 to 1868 – Farms were developed to feed prison populations – Settled along the southeastern coast (Sydney) • Gold was discovered in 1851 and largescale immigration from Europe began European Development • Second episode of “future eating” occurred • English settlers first thought that Australia was a rich “new land” – Biodiversity – Extensive forests – Vast continent • Applied European agricultural practices • Extensive cutting of forests for timber and to clear land for agriculture – Led to erosion and loss of native species European Development • Settlers moved inland in search of better farm land and rivers • Found some areas of fertile volcanic soils but no big rivers • Water supplies were limited by ENSO cycles • Settlement expanded during wet years, failed during dry years Agriculture Today • Still trying to adapt to harsh conditions • Extensive irrigation systems have been developed that take water from rivers • Result has been saline soils and rivers and low stream flow • Naturally saline groundwater limits irrigation options • Also problems with high nutrient levels and algal blooms in rivers Portion of MurrayDarling Basin aquifers that are brackish or saline: • Fractured rock 42% • Sedimentary 49% • Surficial 51% www.mdbc.gov.au • 1991-1992 largest river bloom of bluegreen algae recorded anywhere in the world occurred on Darling River • Extended over 1000 km Water Management Today • Australia today taking a hard-look at how it manages water resources – Discussing what the upper limit might be for country’s human population (now 20 million) – World leader in science of “environmental flows” – Set limits on salinity in Murray-Darling Basin – Program to restore native vegetation • Searching for an alternative to the European model of resource management – Aborigine the new model for living with harsh ecosystem? Future Eating in America • Many parallels with Australia – 2 cycles of predator invasions • Clovis point Indians • European settlers – Megafauna & Indian extinction • Important differences – Resource-rich continent – Relatively short history – Only now are we reaching our limits (water?)